The known bug where it disappears from the Hijack menu happened a couple of times.

Yup, seen this as well. It happens reliably when I start the car while gpsapp is running. Hijack seems to forget that there is a third party app active, but the app is still in it's main loop waiting for intercepted buttons.

The known bug where pressing the left button to zoom-out the map did not do so, instead it rewound the song with no way to stop it. This happened several times.

Same problem. It is hard to figure out where exactly it goes wrong. Maybe the easiest way is to have hijack return an error when an application calls the WAITBUTTONS or POLLBUTTONS ioctl and there are no active redirections. That way the application knows something went wrong and can go register itself in the hijack menu again.

It had a new bug where if you left it up and running for several hours, then for a moment the music from the player stuttered. After that, all front-panel input stopped working and I had to reboot the player by using the POWER button on the remote.

Interesting, I'll see if I can reproduce this.